Prevalence, isolation and identification of histamine forming bacteria in selected stages of supply chain of Yellowfin tuna export industry in Sri Lanka

Abstract

This study aimed to identify histamine-forming bacteria (HFB) and the sources of introduction of such bacteria to recommend control measures to mitigate histamine formation in yellowfin tuna (YFT). Field samples were collected from multi-day boats that landed at Dikkowita, Negombo, Trincomalee and Dondra fishery harbours. Ice from the fish holds (n=63) and chill transport vehicles (n=63), and swabs from the fish holds (n=63), the boat decks (n=63) and the skin of YFT (n=63) were collected. Fish loin samples (n=15), ice samples (n=36) and swabs from the skin of YFT (n=18), floor (n=18) and chill transport vehicles (n=18) were collected from fish processing plants. Presumptive HFB isolated from Nivens medium and Violet Red Bile Glucose (VRBG) agar were screened for histamine forming ability in Tripticase soy broth (TSB) supplemented with 1.0% L-histidine. HFB isolates were characterized by sequencing approximately 1400 bp of the 16S rDNA. Seven isolates that produced histamine in the range of 3000–4000 ppm in TSB isolated from ice samples, and a swab sample collected from the boat deck, were confirmed as Klebsiella aerogens (n=6) and Morganella morganii (n=1) respectively. Hafnia alvei (n=1), Serratia sp. (n=2), Citrobacter freundii (n=1), Rahnella sp. (n=1) and Aeromonas salmonicida (n=8) were also among the isolated histamine forming bacteria. Pseudomonas sp. (n=24) and Shewanella baltica (n=7), which are known as spoilage bacteria were also isolated and showed weak histamine formation. Hence, it is evident that histamineforming bacteria could be introduced into the fish from ice and contacting surfaces. This necessitates the practice of rigorous cleaning procedures and adaptation of proper postharvest handling procedures to minimize contamination of the fish.

The Relationship of Histamine Content in European Pilchard (Sardina pilchardus) with Freshness, Temperature, and Storage Duration

“…Histamine is a biogenic amine responsible for several allergic and inflammatory phenomena (Oktariani et al, 2022;Bose et al, 2023). It is formed as a result of the enzymatic activity of histidine decarboxylase produced by some bacteria, such as Morganella morganii, Raoultella ornithinolytica, Raoultella planticola, Proteus vulgaris, Proteus mirabilis, Klebsiella sp., Enterobacter cloacae, Enterobacter aerogenes, Citrobacter freundi, Serratia liquefaciens, and Serratia fonticola (Tao et al, 2022;Ginigaddarage et al, 2023;Rachmawati et al, 2023), which is accentuated by poor storage conditions (Emborg and Dalgaard, 2008;Abuhlega and Ali, 2022). This leads to the decarboxylation of L-histidine, which is naturally present in the flesh of many species of fish (García-Ruiz et al, 2011).…”